Traynor YBA (JMP type) Recapping

[Guitarist]

So, as I'm not sure if I wish to really keep this classic '72 amp in the JMP tradition - trying to figure out the best way to recap it. I have all the parts shipping. I will be using terminal strips.
With the existing grounding scheme, which works, I a bit concerned that though sounding fine now, might reveal mucho hum with any gain pedals added. I'd like to keep the amp stock for now.
So should I follow again Valve Wizard's grounding upgrade (there's a couple) or maybe a hybrid upgrade. Anyways just running it by you guys!
Photographed, you can see ground points for input, tone, presence, B+ A, and the el34s'.

Also, via the OT, the speaker wires run under the mid-preamp towards the back panel, is this a concern too? Maybe it too low Z to matter.
I've already add a three-wire power cable replete with lock and remove associated cap and polarity switch.

thanks so much.

[Randall]

Not sure, are you asking about recapping the amp, or modding the grounding scheme, which you say is working fine, and you want to keep it stock? I don't see how gain pedals would effect ground hum. Why not just recap it as designed, and then see if you need to change something. My guess is, if it's working OK now with old caps, it will work even better with fresh ones. And sure, there probably are grounding method improvements, but so are there in all the Fender blackfaces, and they all sound pretty freaking good as built.

[The Dude]

^^^^ Agree. Fix it first, then see if it needs ground modifications.

[TomCarlos]

Just a heads up if you decide to mod the amp..... Being a Project Manager by trade, I have learned to utilize a "Change Process" when working on electronics. I make a list of changes that I want and do them incrementally. This will give you test points along the way. Change one or two things at a time. Test the amp at each step. So if something (the amp) stops working, you will know exactly what you did (and where to look for solder problems, wrong wiring connections, etc).

It's great that you took photos. I also do this. I can't tell you the number of times I forgot what wire or component was tied to something else and I did not have a schematic. So I take lots of pictures and save them in a folder along with my notes.

As for changing the ground scheme, do you hear noise, excessive hum, or a problem that would make you want to alter the grounding? As Randall says, your amp might already "sound pretty freaking good as built." Unless you want to tinker, you might be spending time and not seeing any difference. And there is always the possibility you end up worse that what you have now.

[Guitarist]

By "working fine", though vague, I meant as to the design. Actually the choke is gone and hence turning it on at the seller's, produced no sound. So I have to sub in a resistor first.
I am going to recap it, for sure. It just so much work to to recap an amp, as you know that I'd just rather do it once! The amp hasn't seen much use for who knows how long. I doubt my soldering irons are fully up to chassis soldering;(
Years ago, I made a series-lightbulb current limiter for testing and ghetto, cap forming.

[Randall]

I recapped a SVT before lunch yesterday. Not that big of a deal.

[Mick Bailey]

I've recapped a few Traynors, including my own YBA-1A II (since sold). I've never had to mod the grounding and after recapping the amps have all had far less hum (they all had the original stick of dynamite caps) I used low-esr Panasonic radials on tag strip. The amps work just fine with high-gain pedals. I just used my regular solder station for the recap - no chassis soldering needed.

[Enzo]

My take on high gain pedals:
Any increase in hum they make is OUTSIDE the amp. Other than add some exotic signal processing, there is nothing you can do IN the amp to kill hum added to the signal from outside.

[Leo_Gnardo]

I doubt my soldering irons are fully up to chassis soldering;(

You could 1) cut ground leads long when removing the old caps, and solder your new caps to those leads. B: drill holes, put ground leads to solder tabs bolted to the chassis - you're already planning to use terminal strips so why not... or III} Spend a couple bucks on a handy Weller 80W iron. I can tell you, mine is one of the handiest tools I have. Was donated by a woman who used it for years making stained glass panels. It's so frazzled I ordered a spare - but the original still functions despite its disheveled looks. If you do choose to solder to chassis, DO sand or wire brush the soldering zone clean first, DO use ol' fashioned 60/40 tin lead solder, DO use a schmear of Nokorode flux - or, surprisingly a small dab of Deoxit also works well as a flux.

https://www.amazon.com/s?k=weller+80...l_6dxardx11w_e

^^^ choices of Amazon sources for the 80W. Note some have cleverly dropped the price below $25 so you will have to pay shipping (nice job guys!) No matter how you get it, you'll find it's the right tool for the job. 120 & 160W versions also exist. Big solder "guns" don't work so well - some may differ but I've tried and no satisfaction here - it's the big heavy tip on the big "pencil" irons that do the trick.

[Chuck H]

My take on high gain pedals:
Any increase in hum they make is OUTSIDE the amp. Other than add some exotic signal processing, there is nothing you can do IN the amp to kill hum added to the signal from outside.

THIS^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Adding a pedal won't induce hum in the amp because it can't increase the amps gain. Rather, it increases signal gain going into the amp. So, as Enzo said, any hum a pedal adds is coming from the pedal or some other part of the external signal chain.

I had an old YBA that was strangely functional with the original Mallory cap at something like 30yo. This is the one and only case of a cap of that age still being functional that I've ever seen. But I've read (and continue to read) similar reports here. It's always Mallory caps involved! How the hell did they make those things? Probably some horrifyingly carcinogenic proprietary formula that's way outside todays regulations. Along with really high quality control I'm sure. WRT electrolytic caps it seems that amps built with Mallorys in the 60's and 70's are holding up better at the turn of the century than amps made with other brands in the 80's and 90's It seems we lost something. We should go back and find it.

[Guitarist]

Alright that is all good news. Especially, Mick replying that he's "been there" with this type of amp. And it'll be much easier. My first cap attempt was ages back, a Ampeg VT22. That didn't go well but thankfully, I had a great tech from Kelowna BC that redid it all perfectly.
Good idea with the strips bolted down. Maybe I'll upload the process...gotta catch a ferry...!

[g1]

If it has a can cap that is soldered to the chassis, you need a very good joint there for proper grounding. There are lots of tips & tricks available from folks here if that is required.
What is the voltage rating on those bias caps?

[Mick Bailey]

Soldered-in can caps can be difficult. I have a very large iron for those jobs that takes 1/2 hour to come up to temperature and has a massive copper bit. Unless the can is being replaced I find it best to leave it alone and mount smaller, modern caps nearby.

[Guitarist]

If I can get the old can caps off, then I have some larger clamps that perhaps I can resize and use (forgot to add the proper ones to the CEDist order). I'll make a paper template strip first soas to drill the bolt hole in the right place. But who knows maybe the Mallorys are still good! Wouldn't that be something. Though I'll likely tag the other caps to leads from the old ones, the A (B+) can caps will have to go to a good ground spot.
The pair of replacement bias caps are 100uF at 100V.

Good points, thank you.

[Guitarist]

Also those secondary OT speaker wires: should I just tightly twist them? They pass right under the preamp!